Telephone-exchange system



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S. E. WILLIAMS, JR

TELEPHONE EXCHANGE SYS TEM i @WNWUJ'W Aff@ A 2 9 nl h S. B. WILLIAMS, JR

TELEPHONE EXCHANGE SYSTEM Filed June 20. 1921 9 Sheets-Sheet 2 Aug.. 1152 1924. 1,504,297

S. B. WILLIAMS, .JR

TELEPHONE EXCHANGE SYSTEM Filed June 20. 1921 @Sheets-Sheet 3 S. E. WILLIAMS, JR

TELEPHONE EXCHANGE SYSTEM FiledJune 2o. 1921 9 Smets-sheet 4 Auw m, w24? www? S. B. WILLIAMS, JR

TELEPHONE EXCHANGE SYSTEM Filed June 20. 1921 9K Sheets-Sheet 5 y www ,/Wy,

s. B. WILLIAMS, JR

TELEPHONE EXCHANGiE SYSTEM Filed June 20. 1921 9 Sheets-Sheet 6 15045297 $5. a. WILUAMS, JR

TELEPHONE EXCHANGE SYSTEM Filed June 20, 1921 9 Sheet eet '7 y mw m., :i1-2, w24.. www? S. E. WILLIAMS, JR

TELEPHONE EXCHANGE SYSTEM FiedJ e s. B. WILLIAMS, JR

TELEPHONE EXCHANGE SYSTEM Filed June 20. 1921 9 Sheets-Sheet 9 Patented ding. l, 11924,

SAMUEL B. WILLIAMS, JR., F BROOKLYN, NEW YORK, ASSIGNOB, TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed .Tune 20, 1921. Serial No. 478,316.

To all .who/mr t may concern:

Be it known that l, SAMUnL B. lVILLrAMs,

Jr., a citizen of the United States, resid ing at Brooklyn, in the county of Kings, State of New York, have invented certain new and useful Improvements in rTelephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

lThis invention rela-tes to telephone exchange systems and more particularly to systems of the character wherein machine switching devices areemployed for the extension of talking connections.

In telephone systems where the extension of certain classes o f connections involve a plurality of separate offices, the connections in any twok adjacent oflicesl being built up either entirely or in part by means of automatic switches, it is in some cases desirable to have the switches in each of the ofces concerned governed by separate controlling mechanisms correspondingly located in the oflices containing the switches. which they control. y

switches `in the first office involved, for examplein the extension of a connection in cluding only two oflices, are positioned unv der the control of mechanism thereat to eX- line to the distant oliice. In the distant office the selective switches, which participate in the further establishmentof the connec`l tion, are governed by a separate controlling switches in all offices governed from a single controlling mechanism, arises particularly ininteroflice systems where different offices are equipped with selective switching ap-V In other words, the selective tend the connection over an interofiice trunkl mechanism located in the distant office. The expedience of this method of separate con, trol, instead of arranging to have thel trol of a register sender thereat which receives its record over the connection extended from the calling office.

Due to the fact that the impulses, which cause the setting of the register sender at the distant office in accordance with a portion of the complete designation, are transmitted from a subscribers or operators dial, and follow in rapid succession the impulses which govern the setting of the step-bystep selectors in the calling oflice, it is impera@ tive that a register sender be attached to the incoming trunk immediately that such trunk is seized by the last switch in the calling office. Otherwise, part of the impulses intended to be recorded on the sender may be lost or mutilated. Furthermore, due to the importance of having a sender available to serve a calling trunk, it is desirable that all senders provided to handle this class of connections may be arranged foi` universal use and appropriated by all trunks regardless of the fact that a grouping relation normally exists between trunks and senders.

Accordingly, it is one of the objects of the present invention to provide a system of the foregoing character wherein a plurality of register senders are each respectively associated with a plurality of groups of trunks, and normally arranged to serve the trunks of the group to which they are individual, together with means for enabling any one of said senders to serve the trunks of'groups other than the group to which it is normally individual.

,A feature of the invention relates to the provision of a plurality' of groups of senders, one normally individual to and adapted to serve each group of trunks, and means whereby when all senders of the group, normally serving a particular group of trunks, are busy, a sender of some other group may be rendered effective to serve the trunks of such particular group.

A further feature relates to the provision of means whereby the register senders, which normally serve the trunks of their respective individual groups of trunks and, under certain conditions, the. trunks of other groups are immediately connected to such trunks through the contacts ot connecting relays.

Such other and further features as are contemplated in the present invention will become more clearly understood trom the following description and from the appended claims.

In the drawing, Figs. 1 to 9 inclusive, when taken in the order illustrated in Fig. 10, disclose the details of a telephone exchange system embodying the principles covered in this application.

Fig. 1 shows one of a plurality of subscribers lines terminating in an individual switch at the central otlice, diagrammatically illustrated. This ligure also illustrates, in diagrammatic manner, a group selector switch of the step-by-step type and the detailed circuits ot a repeater located in the vsame otlice.

F ig. 2 shows one of a group of interoifice trunk circuits incoming trom the repeater at the distant oice and terminating in an incoming selector switch of the powerdriven type located in the dist-ant oiiice. There i also disclosed in this gure a diagrammatic illustration ot a linal selector switch, which, in cooperation with the incoming switches, establishes connections through to the called subscribers lines. i

1n the rectangular space, set ott by broken lines in the upper part ot Fig. 3, is shown a second trunk terminating in an incoming selector switch belonging to the same group as the trunk shown in Fig. 2, together with certain relays and circuits individual to this trunk. This ligure 'further illustrates tour pairs of multi-contact connecting relays, each pair individual to a group of incoming trunk circuits and the function of which is to connect the senders to a trunk of the group to which such relaysare individual.

In the space set otl:1 by broken lines in the upper part ot' Fig. 4 there is diagrammatically shown one of the trunks ofthe second group of trunks incoming to the distant oiiice and terminating in an incoming switch. Below the broke-n lines this 'tigure illustrates four pairs of multi-contact connecting relays associated with the second group of trunks, each pair cor 1esponding to a pair of relays shown in Fig. 3 and serving a similar purpose.

ln the space set ott by broken lines in the upper part ot Fig. 5, one of the trunks of the third group ot inter-ollice incoming trunks is illustrated, together with certain relays and operating circuits therefor. rlhe remainder of the gure shows tour pairs of connecting relays associated with this third group of trunks and having the same function as the relays shown in Figs. 3 and 4.

Fig. 6 shows a controlling and selecting circuit associated with the iirstgroup of incoming trunks, ot which two are illustrated in Figs. 2 and 3, the purpose ot which. is to connect the register senders to any ot the trunks in this group.

Figs. 7 and 8 show controlling and selecting circuits similar to Fig. 0 and individual respectively to the second and third groups of incoming trunks.

Fig. 9 illustrates, in diagrammatic manner, two register senders ot the group which normally serves the trunks of the first group of trunks, namely that group containing the two trunks shown in Figs. 2 and The system herein disclosed is one in which the extension ot a connection from a calling line to a called line takes place over selective switches of the step-by-step type in al i'irst oiiice, an inter-oiiice trunk to a distant otlice and thence over switches of the power driven character located in the distant otiice. r1`he calling subscribers line is shown terminating in thel brushes 102, 103, 104 oit an individual switch having access to the terminals 105, 106, 107 of trunks leading` to lirstl selector switches. These individual switches may be oi any well-known and approved type. The first selector switch, illustrated by the brushes 108, 109, 110, is or" the well-known step-by-step character arranged to be select-ively operated by impulses transmitted trom the subscribers dial and has access to the terminals 111, 112, 113 ot trunks which lead to the distant ollice. ln the outgoing end of each of these. trunks a repeating mechanism is provided which receives a series ot impulses troni the calling snbscribei"s dial and repeats them over the conductors 121, 122 of the inter-oliice trunk to cause the positioning ot the registers ol' the register sender at the distant otlice in accordance with that portion ot the called designation which determines the setting of the. incoming and final selector switches 224 and 225 to select the called subscribers line.

At the distant oiiice the incoming selector switches, designated generally by the characters 221i-, 300, 400 and 500 and the inal selector switches, one ot which is indicated at 225, are of the revel-tive impulse control power driven type and may be ol the same construction and operation as the one shown in the patent to Graft and Reynolds, No. 1,123,696, issued January 5, 1915.

The sequence switch 210, which controls the changing operation ot the circuits ot the incoming selector switch 224, is ot the same construction and principle as the one described in patent to Reynolds and Baldwin, No. 1,127,808, issued February 9, 1915. The same is true ot the sequence switches 910 and 920 belonging to the register senders' shown in Fig. 9.

The register senders, illustrated. only in Cil part herein, consist of a plurality of regis ters tor recording the designa-tion of called lines, impulse receiving mechanism for positioning these registers, counting relays for controlling the setting of the selective switches in accordance with the designations recorded and the other usual elements. These senders may be of the same general type as the one shown and described in the patent to Stearn and Scudder, No. 1,395,977, issued November 1, 1921.

The incoming trunks 121, 122 from the calling step-by-step ottice are divided at the distant otlice into a plurality ot groups. 1n order to facilitate an explanation oiE the manner of division, it will be assumed that each major group of 120 incoming trunks is subdivided into twelve groups of ten trunks per group. To each of these twelve groups of trunks a group of register senders is assigned to control the connection incom` ing on such trunks. The number of senders assigned to serve a groupof ten trunks will, of course, be determined by the nature of the traHic. ln the present disclosure only two senders have been illustrated as serving each of the several groups. The irst group of ten trunks containing the trunks 121, 122 and 301,302 is accommodated by the group of two senders 900 and 915 shown in Fig. 9. These senders normally serve all connections incoming over the trunks of the group to which they are individual and may be taken for use and associated with any calling trunk in the group. It both senders are idle when a call appears on one of the group of ten trunks, the lirst sender 900 is connected to that trunk, but it this sender happens to be busy at the time then the next sender 915 is taken.

The second group of senders, not shown herein, is assigned to normally serve the trunks of the second incoming group, of which trunk 401, 402 is one. Certain sequence switch contacts 740, 741, belonging respectively to the two senders ot the second group, are shown within the area set oil' by broken lines at the bottom of Fig. 7. In like manner the two senders oit the sec* ond group are, when idle, utilized normally for the purpose of controlling connections extended over the trunks of the second group.

Similarly, a group oi two senders will be provided or'normally serving the calls on incoming trunks of the third group, one ot which trunks is shown in Fig. 5. For each of the remaining nine groups of trunks a corresponding group of register senders is provided iior normally serving calls incoming thereon.

The register senders are arranged to be connected to the trunks by mea-ns ot multicontact connecting relays. lThe coordinate principle of selection is employed, there being a group relay for each group of trunks and a units relay tor each of the trunks in the group normally served by said senders. For example, the relay 304 is individual to the first group of trunks and connects these trunks with the irst sender 900 ot the group of senders. Relays 606, 607, 608 are individual to the first three trunks respectively oli' the group of ten. There will, of course, be a units relay :tor each of the remaining trunks. The group relay 304 is provided with a set or contacts for each ot the ten trunks of the group, whereby, when this relay is energized, the three controlling conductors individual to each trunk are extended through the arma tures and contacts of such relay. At the same time the particular units relay, individual to the trunk with which it is desired to associate the sender 900, is energized, whereby the three controlling conductors, such as conductors 227, 228 and 229, are further extended over the armatures and contacts ot said relay to the register sender 900. The multi-contact group relay 305 is also individual to the lirst group of ten trunks and operates to associate the second sender 915 of the lirst group ot senders with these trunks. It operates to extend the controlling conductors of all ten trunks through to the contacts of the ten units relays individual to the second sender of which three are shown, namely relays 6.13, 614 and 615. The relays 613, 614 and 615 are, like relays 606, 607 and 608, respectively individual toA the ,several trunks of the, group. Consequently, the energization or relay 305 and the energization of the particular one of the ten units relays individual to the calling trunk serves to extend the three controlling conductors to the second register sender 915. Should other register senders be provided for each group there would also be a group relay similar to relays 304 and 305 t'or each additional sender, together with a set ot individual units-relays similar to relays 613, 614 and 615.

The selection oi the group relays 304, 305, etc., is initiated by the presence of the calling condition ot one of the incoming trunks oi the group with which these relays are associated and depends upon the busy or idle condition ot the register senders normally serving that group; for instance, if a call occurs on one of the incoming trunks and the first register sender 900 is idle, the group relay 304 is operated, but ii the tirst sender is busy and the second sender 915 is idle, then the group relay 305 is energized instead. The selection ot the proper one of the ten units relays depends upon the units designation oi the trunk on which the call appears and also upon the particular sender which is to be associated with such trunk. It the call appears on the first trunk of: the group and the rst sender is idle, then the No. l units relay G00 is operated in conjunction with the group relay 304, whereas if the third trunk calls instead, the No. 3 units relay 608 becomes energized. On the other hand, should be first sender be engaged when a call is extended over trunk No. 1, the No. 1 units relay 613 is operated in conjunction with the group relay 805 individual to the second sender, and so on.

Considering` the second group of ten incoming trunks, or which one is shown diagrammatically in Fig. 4, the senders of the group normally serving these are arranged to be associated in identical manner. Relay 406 is the group relay individual to the second group of trunks, through the armature contacts of which the controlling conductors for each of the ten incoming trunks are extended to the contacts of the units relays individual to thefirst sender oi the second group of senders., The multi-contact group relay 407 is alsoindividual to the second group of trunks and has for its function to associate the second register sender of the second group with any of the ten trunks. rlhe ten units relay 706, 707, 70S, etc. are each individual to the ten trunks of the group and also to the first register sender.

The same arrangement is true with respect to the third group of ten trunks, one of which 501, 502 is shown in Fig. 5. Here the two group relays 510 and 511, associated with this group of trunks, servel respectively for associating the two register senders of the third group with the ten trunks of the third group of trunks. The same plan may be extended throughout the twelve different groups, according to the assumption, or to as many groups as the system embraces. Only three complete groups have been shown, however, inasmuch as a further duplication. of the disclosure is unnecessary for an understanding oi the invention.

According to an important feature of this invention4 a circuit relation between the several individual groups is employed whereby the register senders orl the several groups, which normally serve the trunks with which they are associated, may also be taken for use under certain conditions in connection with the trunks of any 01"' the remaining groups. That is to say, should a connection be extended over one of the trunks in the rst group at a time when both register senders 900 and 915, normally serving that group, are busy, the first idle sender in the succeeding groupmay be taken for use: and associated with the calling trunk. Should the .first sender and all succeeding senders in the second' group likewise beV busy at the time, then the first idle sender in the third group may be taken for use. Such an arrangement itA will be seen enables a normal individual association of the senders with the different groups of trunks and at the same time permits a universal use of all senders in eonnection with the trunks of all groups. To this end the first group of trunks 121, 122 and 301, 302, etc., in addition to being provided with their respective group relays 304 and 305, are also provided at each. of the remaining eleven groups of trunks with corresponding group relays. At the second group thevrelays 404 and 405 are individual to the first group of ten` trunks and serve to associate respectively the two senders normally allotted to the second group oft trunks with the trunks of the first group. At the third group the relays 504 and 505 are individual to the first group o'f trunks and operate respectively to associate the two senders normally allotted to the third group olE trunks with the trunks ot the first group. Similarly, the second group of ten trunks is provided at the first group with the two ndivdual group relays 306 and 307 which. serve respectively to associate the senders 900 and 915 with the trunks ot said second. group. The same relation exists throughout all the remaining groups of trunks, namely that every group has at every other group of trunks as many individual group relays thereforas there are senders in a group of senders. It will be noted that the conductors 227, 22S and 228 of the first trunk in the lirst group which lead to the armatures ofi the group relay 304 also lead to. the armatures of each of the group relays 404, 504, etc., individual to the first group of trunks at all remaining groups. In like manner these. three conductors, which extend to the armatures ot relay 305, are n'iultipled lo corresponding armatures ot the lgroup relays 405,505, etc. at all other `groups. The, same relation of multiple wiring` between the armatures of the group relays throughout the entire twelve groups also exists with rospect to all other trunks.

Consequently, should a connection be extended, or example, over the first trunk 121, 122 ol" the first group when both senders 000. 915 normally used in connection with `this group are bnsy,a condition is lnought about for the energization of group relay 404 individual to the first group o'' trunks at the, second group, and for the energizatimi of' the units relay 706 individual to the first sender of the second group provided this sender is idle. The calling trunk is thereby connected through the contacts of relay 404 `and relay 706 to an idle sender in the second. group and this sender thereupon operates to control the establishment of the connection. If all senders in the second group are busy as well as all senders in the first group, then the initiation of a call on a trunk in the lirst group of trunks causes the energization of the relay 5041 at the third group of trunks and the energization of the corresponding units relay individual to the firstidle sender in the group normally serving the third group of trunks, and this idle sender is associated with the calling trunk.

By the use ot these coordinate connecting relays it will be observed that the register senders are instantaneously connected to a trunk line upon the extension of the connection over that trunk to "the distant oirice whether the sender talren belongs to the group normally serving the group containing the calling trunk or to some other group ot senders. The necessity of a quick attaclr y ment oi the senders to the trunksk arises from the tact that only a short interval ot time is available between the completion ot trunk limiting in the calling otce and the transmission of the neXt succeeding series of inipulses from the calling subscribers dial. rllhe sender must be attached before this series of impulses is sent in order that they may be properly recorded thereon.

After all series of impulses have been transmitted over the trunk and recorded on the registers of the associated sender, this sender becomes eective inthe well-lnown manner to control the selective movements of the incoming selector switch 224 and the final selectorl 225 to complete the extended connection to the terminals of the called line.

A. general description having thus been given ot the grouping arrangement utilized in this system, it is believed that a more thorough understanding is to be had of the invention from a detailed description of the operating circuits.

For this purpose it will be assumed that the subscriber of line in the originating office desires to obtain a telephone connection with the subscribers line 200 in the distant office. Upon removing his receiver from the switch hook the subscriber at substation 100 causes the operation ot the individual switch, which automatically drives its brushes 102, 103, 104 to the terminals 105, 106, 107 of the trunk leading to a first group selector switch. rllhe subscriber thereupon manipulates his sending dial 101 to transmit a series ot impulses causing the first group selector to operate in a step-by-step manner to select and seize the terminals 111, 112, 113 of an outgoing trunk 121, 122 leading to `the desired distant oitice which is equipped with switches of the power driven type. Immediately that the brushes 108 and 109 arrive upon the terminals 111, 112 o'f the trunk, a circuit is closed from battery through the upper winding of relay 114, upper normal contacts of relay 115, terminal 111, brush 108, terminal 105, brush` 102, thence'over the loop oi' the calling line and returning by way of brush 103, terminal 106, brush 109,

terminal 112, normal contacts at the inner lower armature of relay 115, lower winding ot relay 114 to ground. Relay 11a closes a circuit for relay 116. liVith relays 11a and 116 energized a circuit is established from battery through the left-hand winding of relay 203 at the distant oiiice, lower back contact o'f relay 202, contact ot' sequence switch spring 207 (1 -l- 9), conductor 122, concluetor 123, lower contact ot relay 1111, righthand winding of relay 119, normal contact at the lower armature of relay 115, conductor 120, upper winding of relay 118. back contact of relay 117, uppermost contact ot relay 116, conductor 121, contact ot spring 206 (1 9), upper back contact of relay 202, winding of retardation coil 201 to ground. lt will also be noted that the relay 116 upon energizing completes a circuit through the lower winding of relay 118. Relay 118 is so constructed as not to operate due to the flux created by its lower winding alone, `and is also arranged such that it fails to operate when the lower winding is energized and when current tlows through the upper winding in a given direction. The current in thecircuit `inst traced over the trunk 121, 122 through the upper winding ot' differential relay 118 is in the wrong direction for causing the operation ot said relay. Consequently, relay 118 remains inert.

The relay 203 at the distant ofiice upon energizing closes a circuit tor relay 209. Relay 203 also closes a circuit from ground through its outer contact and armature, lett back contact of relay 208, conductor 226, winding of relay 600, winding of relay 612 to battery. The relay t300 is individual to the first trunk in the group of ten trunks, namely to the trunk- 121, 122. 1n a similar manner relay 601 is individual to the second trunk 301, 302 in the first group, while relay 002 is individual to the third trunk. The remaining relays individual to the remaining trunks have not been shown. ln the circuit above traced the relays 600 and G12 become energized and a circuit is thereupon established. from battery to the lett-hand winding of relay 603, front contact ot' relay 600, outer left contact of relay 618, outer left contact of relay 019, conductor G30, and thence to the conductor similarly identified in Fig. 8, to ground at the outer right back contact ot relay 800.

It will be well to explain' at this point that where only three groupsot trunks have been illustrated in the present disclosure instead ot all twelve groups, it isassumed that the several conductors, which terminate onthe lett-hand side of Fig. G, are joined in corresponding vconductors terminating on the right-hand side ot Fig. 8. Several ot these conductors, namely those most likely to be considered in the following discussion, are terminated in small circles bearing letters oi relay 609.

the alphabet in order -to facilitate their identity.

The reason for extending the energizing circuity of relay 603 through the armature and contact of relay 800 of the preceding group is to test the condition of such preced ing group-to insure that it is not in the act i outer left Contact of relay 619, and thence to ground at relay 800 as traced. Relay 618 operates in series with relay 603.

It is taken for granted that the rst sender 900 is idle at this time. Relay 618 in operating closes a circuit from ground through its outermost right contact, right armature and back contact of relay 619, inner right armature and back contact oli' relay 621, conductor 625, conductor 634, contact 912 of the sender sequence switch 910 closed in position 1, conductor 635, left back contact of relay 610, winding of relay 609 to battery. Relay 609 is the allotting relay individual to the sender 900 and through its armature contacts prepares circuits to each or the group relays 304, 306, 310, etc. individual to the first group of trunks. Relay 609 in operating also establishes a circ-uit from battery through the winding and contact of said relay, conductors 637 and 638, outer left armature and back contact of relay 621, Winding or' relay 619 to ground at the outermost right contact of relay 618. Relay 619, included in this ci-rcuit, does not operate in view of the shunt closedl around its winding through the lett armature and back contact of relay 610. 1n addition to preparing circuits through t-he windings of group relays 304, 306, 310, etc., the allotter relay 609 also prepares circuits to each of the ten units relays 606, 607, 608, etc. individual to the first sender 900. A circuit may nowbe traced from ground through the middle right contact of relay 618, conductor 626,

lcontact 638 of relay 609, conductor, 639,

Winding of relay 304 to battery. Relay 304 operates and locks in a` circuit from battery through its winding and right contact, conductor 322 to ground at the contact 640 of Furthermore, a circuit is closed from ground through the inner right Contact of relay 618, left Contact of' relay 603, conductor 641, contact642 of relay 609, winding of relay '606 to battery. rllhe units relay 606 locks in a circuit from battery through its Winding and right contact, conductor 322 to .ground at contact 640. lllith both the group relay 304 and the units relay 606 energized, the three controlling leads 227, 228 and 229 of the trunk 121, 122 are extended through to the register sender 900. Therefore, a circuit is established from ground through the outer right contact of relay 209, lower lett contact of spring 215 (1-l-9), lelthand winding of relay 208, conductor 229, contact 323 of relay 304, conductor 318, outermost left contact of units relay 606, winding of relay 610 to battery. Relays 610 and 208 become energized. Relay 208 locks in a. circuit from battery through its right-hand winding and inner right contact, outer right contact of relay 209 to ground. Relay 208 at its left back contact opens the energizing circuit of relay 600 individual to the trunk 121, 122, permitting this latter relay to rclease.

It will bel noted that at the time relay 209 operates a circuit is completed Vfrom battery through the winding of relay 212, upper right contact of spring 215 (Ll-1.1,), outer right contact of relay 209 to ground. Relay 212 operates in this circuit.

Relay 610, which also operates in series with relay 208 at its left armature and contact, opens the shunt around the winding of relay 619 permitting this latter relay to operate. Relay 619 upon operating opens the circuit for relays 603 and 618 and these relays deenergize. Relay-618 in turn opens the circuit of relays 609 and 619 which also become deenergized. IRelay 609 cannot again operate since its energizing circuit is held open at the left back Contact of relay 610. Relays 304 and 606 are now held energized in their locking circuits which extend to ground at the right front contact of relay 610 instead of through the contact 640 of' relay 609.

The register sender 900 has thus been attached to the trunk 121, 122 and the operations involved in the connection have taken place within the very brief interval following the closure of the trunk at the repeater in the' calling ollice. lllhen thc calling subscriber manipulates his dial 101 to transmit the next series of impulses corresponding, for example, to the second digit in the calleddesignation, the relay 114- is deenergized and energized in succession to cause the repetition of the impulses over the outgoing trunk circuit. Upon the first opening of the subscribers line relay 114 releases its armatures and a circuit is closed from ground through the upper back contact of said relay, inner upper contact olf relay 116, winding of relay 117 to battery. Relay 116 being slow to release does not become deenergized during the intervals in whichits circuitis open at the upper Vlront contact of vrelay 114 in the transmission ot impulses. Likewise, relay 117 is of the slow to release character and remains operated during the brief intervals in which its windingis open at the upper back Contact ot relay 114.

lill

lielay 114,: at its lower contact opens the circuit traced over trunk 121, 122 through the left-hand winding of relay 203. At the time relay 20S operates it closes a circuit from battery through the two windings of relay 200 in series, left front contact of relay 200, vouter contact of relay 203 to ground. rlhe relay 203 is so constructed that the right-hand winding produces a differential effect. lilVhilQ the flux set up due to the energization of the right-hand f winding is not suflicient to differentiate the finir caused by the left-hand winding, it does operate as soon as the circuit of the lefthand winding is opened to effect a quick release of the armatures. Consequently, upon the opening of the operating circuit through the left-hand winding of relay 203, the relay innnediately retracts its armatures. Relay 209 being' slow to release does not ret fact its armatures during the brief intervals that its circuit is open at the inner front Contact of relay 208. A circuit is now completed from ground through the inner back AContact of relay 203, inner contact of relay 209, conductor 227, contact 3211 of relay 304, conductor 316, innermost left contact of relay 606, conductor 6333, left-hand winding of relay 901 to battery. Relay 901 operates and completes a circuit from ground through its contact, brush 904; of the register control switch (position 1), winding of register stepping magnet 906, winding of slow-to`- release relay 911 to battery. Magnet 906 becomes energized preparatory to advancing the brushes of the first register one step forward.

One of the brushes and the terminal bank with which it cooperates for the first regis ter is designated by the character 916. One of the brushes of each of three succeeding registers and its cooperating terminal bank is also diagrammatically illustrated in the drawing. These are shown at 917, 918 and 919, respectively. lt` is understood, of course, that there will be as many registers as desired. For controlling the successive association of the impulse relay with the several registers and for controlling other functions involved in the operation of the sender, a register control switch is provided which, like the registers themselves, consists of a single motion step-by-ste switch. Three. of the brushes 903, 904 and 905 and their cooperating terminal banks are shown for the register control switch. These brushes are stepped forward by a stepping magnet 902 and are arranged'to be advanced upon deenergization of the magnet.

The slow-toerelease relay 911, which, as above described, becomes energized in series with theJ stepping magnet 906 for the first register, completes a circuit from ground through its contact, winding of magnet 902 to battery. The magnet 902 energizes and prepares to advance the brushes 903, 904C and 905 forward one step upon deenergization. At the end of the first impulse the subscribers line circuit is closed and relay 114C again energizes. Relay 203 is now operated in a circuit from battery through its left-hand winding, thence over the conductor 122, as hereinbefore traced, conduc-tor 123, lower contact of relay 114, conductor 124, front contact of relay 117, uppermost contact of relayt 116, conductor 12'1, and thence to ground through the retardation coil 201. lThis circuit excludes the upper winding of the differential relay 11S, but this relay still. remains deenergized due to the fact that current flowing through the lower winding thereof is insufficientto operate the same. lielay 208 on operating opens the circuit of the relay 901 at the sender, which in turn deenergizes and opens 1 the circuit through the stepping magnet 906 and relay 911. Magnet 906 deenergizes and advances the brushes of the first register, of which brush 916 is one, forward to their first position contacts. Relay 911, however, being slow to release maintains its armature attracted. This procedure continues for each impulse in the series until all impulses have been completed from the calling subscribers line. lifter the proper interval has elapsed following the last closure of the subscribers line, during which time relays 114 and 203 are maintaining their armatures attracted, the slow-to-release relays 117 and 911 become deenergized. lielay 117 establishes the` )reviously traced circuit over the trunk including the upper winding of the differential relay 118 and the left-hand winding of relay 203. Current still flows in the wrong direction, however, to cause the energization of the differential relay 118. Referring to the sender the relay 911 upon deenergizing opens th-e circuit of the register control stepping magnet 902 4which releases and advances the brushes 908, 904 and 905 on to their second position terminals.

During the transmission of the next series of impulses, representing the next digit in the called designation, relays 114, 203 and 901 respond in the manner previously described and the stepping magnet 907 is successively operated to advance the brushes of the second register from one position to another. 'llhe circuit for magnet 907 extends from ground through the contact of relay 901, brush 904- (position 2), winding of magnet 907, winding of relay 911 to bat-` tery. Relay 911 remains energized during the transmission of impulses, holding the circuit closed through the winding of magnet 902. it the end of the impulse series the second register has been set in its proper position and the slow-to-release relay 911 becomes deenergized to advance the register control switch into its third position. Likewise, 'for each of' the following series of impulses representing` the remaining digits of the called designation, the corresponding registers ci the sender 900 are selectively positioned. Alter the subscriber has cornpleted his dialing' operation, the slow-torelease rela-y 117 deenergizes and the circuit ot the trunk conductors 121, 122 is established including the lett-hand winding ot relay 203 and the upper winding of the differential relay 11S.

Following the completion of the setting oi' the registers ot the sender, the controlling' sequence switch 910 is advanced to aposition tor establishing` `the fundamental circuit for conl'rolling` brush selection at the Aincoming selector switch 2211. The fundamental circuit may be traced from battery through the winding` of relay 213 (Fig. 2), lower right contact of spring 219 (1-1-10), upper left contact et said spring (1), right contact oi spring 214- (ld-Q), inner left front contact of relay 212, outer right contact oi: relay 20S, conductor 22S, contact 25 of relay 30d, middle lett contact ot relay 606, conductor G32, Contact of spring 913 of sequence switch 910, contact of counting relay 921, winding o stepping relay 91d to ground. Relay 21.3 becomes energized and closes a circuit from battery through the winding of sequence switch magnet 210, contact of spring 217 (1), inner contact of rela7 218 to ground, driving said sequence switch out of position 1 and into position ln position 2 a. circuit is prepared trom battery through the winding or the updrive power magnet 211, contact ot spring 218 (2), inner contact of relay 213 to ground. ln the well-known manner the power magnet 211 causes the brush shalt or the incoming selector switch 22d; to be driven upwardly 'for the purpose of determining the selection of the proper set of brushes. The stepping` relay 914, which operates intermittently in the fundamental circuit. causes the counting relays to be successively energized in accordance with the registration on the registers, until linally the fundamental circuit is opened by counting relay 021 at which time the brush shaft has reached a position for the select-ion of the proper set ot brushes. The relay 213 now becomes deenergized and opens the circuit ot power magnet 211, and also in the well-known manner causes the advance of sequence switch 210.

Following the brush selection, the incoming switch is caused torpertorm its group selecting operation and thereafter trunk hunting ensues and a trunk is chosen leadingto an idle final selector switch 225. Brush selection tens and units selections next proceed at the linal switch 225 under the control of the register solider' and the connection is extended through to the terminals of the called subscriberls line 200.

During the period in which the register' sender is attached to the incoming` trunk and is positioned by impulses transmitted from the originating orlice, and also during the selective movements of the incoming and iinal switches, the sequence switch 210 is in its successive positions l'rom 1 to 9. Following` the completed extension oi' the connection the sequence switch 210 advances out ot position 9 into its talking position` which may be assumed as position 1G. On leaving position 9 it is to be noted that the contacts ot springs 206 and 20T are open, whereby the circuit ot relay 203 now extends from battery through thc lett-hand winding thereof, lower back contact of relay 202, lower left-hand winding of repeating coil 20-1, conductor 122 to the originating o'lice and returning by way of conductor 121, upper lett-hand winding of repeating coil 201, upper back contact of relay 202, winding of retardation coil 201 to ground. The left-hand windings ol' the repeating coil 20-1- are thus included in the talking circuit, having been shunted out during the transmission of impulses by springs 206 and 207 in order to obviate their detrimental effect upon the operating impulses.

lWhen the called subscriber responds by removing his receiver from the switch hook, a circuit is established in the well-known manner for the operation of the supervisory relay 205. Relay 205 closes a circuit for rclay 202 which becomes energized and modifies the circuit of relay 203 in such a manner that battery is now connected through the lett-hand winding of this latter relay to the conductor 121, instead ot as originally to the conductor 122. This reversal of current over the trunk and through the upper winding ot diiiferential relay 11S produces acumulative elt'ect in said relay whereby it receives sufficient energy to attract its armatures. l'lelay 118 upon operating completes a circuit 'from ground through its lowermost contact and winding of relay 115 to battery. Relay 115 operates and modiiies the circuit o1a relay 114 so that current now flows trom battery through the upper winding ot relay 114, inner lower armature and contact of relay 115, terminal 112, brush 10Sl,thence over the lower side ot the talking circuit through the loop of the calling subscribers line and returning over the upper side ot' the talking circuit to the terminal 111, contact and upper armature of relay 115. lower winding of relay 1141 to ground. This reversal of current may be utilized in the wellknown manner for operating a polarized message register' individual to the calling subscribers line.

At the termination of conversation the i subscribers replace their receivers on the of relay 618.

switch hooks and all switches utilized in the establishment of the connection are restored to their normal positions in the `usual manner.

Should the rst sender 900, which normally serves the first group of ten trunks, be busy when the connection is extended over trunk 121, 122, then the next sender 915 of the group is taken for use provided the same is idle. The same, of course, is true regardless of what particular one of the ten trunks of the first group receives the call, and in order to illustrate this it will next be considered that the call from the originating otlice was extended over the second trunk 301, 302 of the group to the incoming selector switch 300 in the distant oflice and that sender 9.00 is busy at the time. Immediately that the connection is extended over trunk 301, 302, a circuit is closed as previously traced for the left-hand winding of relay 303, which, it will be noted, corresponds to relay 203 of the lirst trunk. Relay 303 operates and closes a circuit for relay 309. Relay 303, furthermore, establishes a circuit from ground through its outer right contact, left back contact of relay 308, conductor 314, winding of the second. units relay 601, individual to the second trunk in the group 301, 302, winding of relay 612 to battery. Relay 601 closes a circuit from battery through the left-hand winding of relay 604, front contact of relay 601, back contact of relay 600, outer left contact of relay 618, outer left contact of relay 619, conductor 636, thence to conductor 636, Fig. 8, outer right back Contact of relay 800 to ground. Relay 604 operates and closes a circuit from battery through its right-hand winding and right front contact, right back contact of relay 603, Winding of relay 618, outerl left contact of relay 619, conductor 636, and thence to ground as traced. Relay 618 operates and establishes a circuit from ground through its outermost right contact, right armature and back contact of relay 619, inner right back contact of relay 621, conductor 625, conductor 634, upper contact of spring 912 (2-1-18) (the sequence switch 910 being in some position other than position 1 due to the fact that sender 900 is busy), left contact of spring 934 (1), conductor 935, right back contact of relay 616, winding of relay 617 to battery. The allotting relay 617, individual to the second sender 915, is thereupon energized and closes a circuit trom battery through its winding and contact, conductor 638, outer left back contact of relay 621, winding of relay 619 to ground at the outermost right contact Relay 619, however, remains deenergized since its winding is shunted by the direct circuit to ground closed through the right back contact of' relay 616. Relay 617 attracts its armatures and prepares circuits for each of the group relays 305, 307, 311, etc., individual to all groups of incoming trunks. Relay 617, furthermore, prepares circuits for each of the ten units relays. 613, 614, 615, etc. individual to the second sender 915. A circuit is now established from ground through the middle right contact of relay 618, conductor 626, contact 642 of relay 617, conductor 643, winding of group relay 305 to battery. Relay 305 operates and locks in a circuit from battery through its winding and right contact, conductor 315 to ground through the contact 644 ofrrelay 617. A circuit is` also closed from ground through the innermost right contact of relay 618, left contact of relay 604, conductor 645, contact 646 of relay 617, winding of the No. 2 units relay 614 to battery. Relay 614 operates and locks in a circuit from battery through its winding and left contact, conductor 315 to ground through contact 644 of relay 617.

With relays 305 and 614 operated the second register sender 915 of the group is connected to the second trunk 301, 302. A circuit is closed from ground through the outer contact of relay 309, conductor 330, thence, as described in connection With the first trunk shown in Fig. 2, to conductor 331, left-hand winding of relay 308, conductor 329, contact 332 of relay 305, conductor 333, outermost right contact of relay 614, winding of relay 616 to battery. Relay 308 becomes energized and opens the circuit above traced for relays 601 and 612; causing` these relays to become deenergized. Relay 616 also operates and removes the shunt from around the winding of relay 619. Relay 619 thereupon attracts its armatures and in so doing opens the circuit of relays 604 and 618. These relays both deenergize and re.- lay 618 in turn opens the circuits of relays. 619 and 617. Relays 617 upon deenergizing opens the original holding circuits of relays 305 and 614, but these relays remain locked in the circuits previously traced through their winding and contacts to conductor 315 from whence it leads to ground through the 11 5 left front contact of relays 616.

The impulse series set over the line from the calling subscribers station now operate the relay 922 at the sender 915, which in turn causes the successive operation of the stepping magnets 927, 928, 929 and 930 to position the registers in the sender in accordance with the digits of the desired designation. `The slow-to-release relay 931 serves in conjunction with the stepping magnets to cause the progressive advance of the brushes 923, 925 and 926 of the register control switch. The sender' 915 thereafter becomes eiiective to cause the settin of the incoming selector switch 300, an a' final la@ tirs't trunk 121, 122, for example, in the first group When both register senders 900 and 915 normally serving that group are busy. In thls instance the start circuitl tor the energizatlon of anallotting relay 1s extended: through to the group of senders'normally serving the second group of trunks. The extension of the connection over trunk 121, 122 causes, in the manner previously 1X- plained, the energization of the No. 1 units relay 600. Relay 600 operates and prepares a circuit from battery through the letthand Winding of relay 608, front contact ot relay 600, outer left contact of relay 618, outer left contact of relay 619, conductor 636, and thence to ground at the outer right back contact of relay 800. Relay 603 energizes and a circuit is closed trom battery through the right-hand Winding and right front contact of relay V603, ufinding of relay 618, outer left contact of relay 619, conductor 636 to ground as described. Relay 618 operates and completes a circuit 'from ground through the outermost right con tactofsaid relay, right-hand armature and Aback Contact of relay 619, inner right back 'contact of relay 621, conductor 625, conductor 634, upper contact of spring` 912 right contact of spring 984 (2-1-18), conductor 936, conductor 648, inner left Contact of relay 19, inner lett contact of relay 718, conductor 714, normal contact at the right-hand armature of relay 619, left back Contact of relay 622, Windingof relay 620 to battery. The operation ot relay 620 indicates that the first group ot trunks is in the act of appropriating a sender of the second group for use. Consequently, should a call occur o n af trunk in the second group immediately subsequent to the operation of relay 620, the energizingl circuit of relay 718 would be held open at the outer right back contact of relay 620, delaying the call in the second group until it has been` determined which one of the senders of the second group of senders is to be taken for use in connection yvith the first group of trunks.Y It will be remembered that the circuit hereinbefore traced for the corresponding relay 618 ot the lirst group extended to the outer right back Contact of relay 800 in the third group, Which, herein assumed, is the group preceding the irst group. As explained, the reason for this is to prevent the relay 618 froin'op- Yeiating provided the preceding groupY ot "trunks is' about tov appropriate one of the senders 900 and 915 for use.

Relay 620 upon operating completes a circuit 'from ground through its outer right front cont-act, conductor 649, Winding of relay 711-to battery. Relay 711 attracts its armatures and extends the several control conductors 625, 626, 627, 628, etc. ot the first group through to the correspoiuling` control conductors 725, 726, 727, 728, etc. ot the second group. A circuit is thereupon closed, from ground through the outer right. conA tact oit relay 618, right armature and back contact ot' relay 619, inner right contact ol` relay 621, conductor 625, conductor 634, upper contact ot spring 912 (2448), righi. contactI of spring 934 (2-1-18), conductor 936, outer right contact ot relay 621, con` ductor 647, Contact 713 ot' relay 711, con` ductor 725, conductor 715, upper contact ot spring 740 (1) ot the controlling sequence .switch of' the first sender normally serving' the second group ot trunks, conductor 716` lett. hack contact ot relay 71.0, winding` o1: allotting relay 709 to battery. Relay 709 operates and closes a circuit trom battery through its winding and right contact, cou ductor 717, contact 720 or' relay 711, con-- ductor 650, inner lett contact ot' relay 621, outer le't't back contact ot' said relay, ivinding of relay 619 to ground at the outermost right contact ot' relay 618. Relay 619, however, docs not energize. in this circuit so long as its Winding is shunted by the circuit previously trace-d through the lett hack contact of relay 710. Thel allotting relay 709, upon attracting its armatures. completes a circuit 'trom ground through the middle right contact of relay 618, conductor 626, Contact 721 ot relay 711, contact 722 ot relay 7 09, conductor 7 23, winding ot group relay 404 to battery. Relay 404 operates and locks in a circuit. trom battery through its Winding and right contact, conductor 108, contact 724 ot relay 709, to `ground. second circuit is completed Vtrom ground through the innermost right contact o relay 618. lett contact ot relay 60?), conductor 611, Contact 730 of relay 711, contact 731 ot relay 709, Winding ol No. 1 units relay 70o to battery. Relay 706 operates and locks through its right Contact to the grounded conductor 408. Following the operation ol relay 706, a` circuit is closed trom lground through the outer contact ot relay 209, lower 'lett-hand contact ot sprinfV 21.6 (1+ 9), left-hand Winding ot relay 208, con`v ductor 229, contact 408 ot relay 404, con- `du'ctor 409. outermost left contact ot relay 706, Winding of relay 710 to battery. Relay 710 operates and opens the shunt circuit which has been preventing` the energization of relay 619. Relay 619, theretoi'e, operatesV in series with relay 709. Relay 619, in the manner previously described, opens the eircuit of relays 603 and .618 which become deenergized` relay 618 in turn opening the circuit of relays 619 and 709 permitting them to deenergize. Relays 612 and 600 re` tract their armatures at the time relay 208 l lo operates in the circuit just traced includ ing relay 710. At the time relay 619 oper-` ates it modifies the circuit of relay 620 as follows: battery, through the winding' of relay 620, left back contact of relay 622, make-before-break contact at the right-hand armature of relay 619, outermost right contact of relay 618 to ground. Consequently, relay 620 remains operated to maintain the operation of relay 711 during the period that relay 619 is energized and until relay 618 becomes deenergized. Immediately, however, that relay 618 retract-s its armatures, relay 620 releases and permits the release of relay 711. Relay 709 upon deenergizing opens the holding circuit of relays 404 and 706, but these relays remain operated in a new holding circuit closed over conductor 403 to ground through the right frontcontact of relay 710.

rlhe control conductors 227 and 228 of the first trunk 121, 122 are now extended by way of contacts 412 and 413 of relay 404, conductors 414 and 415, innermost and middle left contacts of relay 706, conductors 732 and 733 to the selected sender. This sender is next positioned in accordance with the incoming` impulses and functions to determine the selective operations of the incoming and final switches to complete the establishment of the connection to the dcsired called line.

Should the rst sender normally serving the second group of trunks be busy as well as both senders 900 and 915, which normally serve the first group of trunks at the time the call appeared on one of the trunks of the first group, then the starting circuit is extended through'to the second sender of the second group. This starting circuit leads, as above explained, from ground through the outermost right contact of relay 618, right armature and back contact of relay 619, inner right back contact of relay 621, conductor 625, conductor 634, upper Contact of lrelay 912V (2 -l- 18), right contact of spring 934 (2+ 18), conductor 936, outer right contact of relay 621, conductor 647, contact 713 of relay 711, conductor 725, conductor 715, lower contactot spring 740 (2+ 18), left contact of spring 741 (1) of the sequence switch controlling the second register sender, conductor 735, right back contact of relay 736, winding of allotting relay 737 to battery. The relay 737 functionsin the same manner and for the same purpose as relays 709, 617 and 609, hereirrbefore described. Should it happen that all senders in both the first and second groups were busy at the time a call occurred on one of the trunks in the first group, then a sender in the third group is chosen it one. is busy, and igt not, in some succeeding group by the saine process as that already explained in detail.

it might happen that there were idle senders in thel group normally serving the group of trunks at the time a call is made therein, but for some reason or other the idle sender fails to be attached to the calling trunk. lf, therefore` an idle sender is not associated w-itlr a calling trunk within a predetermined interval of time following the extension of a connection over such trunk, a condition is brought about for testing the next succeeding group of senders and choosing an idle one therein for use. t `the time the call is extended over the trunk 121, 122, the relay 612, which is common to all of' the ten trunks in the group, is operated in series with the units relay 600. Relay 612 also operates in series with any of the remaining nine units relays. Relay 612 completes a circuit from ground through its contact, conductor 651, thence to conductor 651, Fig. 8, inner right back contact of relay 800, which relay it will vbe recalled is individual to the preceding group, conductor 652, thence to conductor 652, F ig. 6, right back contact of relay 624, winding of relay 623 to battery. Relay 623 operates and closes a circuit from ground over conductor 652, front contact of relay 623, winding of relay 624 to battery. Relay 624 on operating opens the circuit of relay 623. Relay 623, which is slow to deenergize, retracts its armature after the lapse of a given interval of time. Upon the restoration of relay 623, relay 624 remains operated in a locking circuit from battery through its winding and right front contact to the grounded conductor 652. A circuit is now completed `trom ground over conductor 652, bac-k contact of relay 623, inner left contact of relay 624, winding of relay 622 to battery. Relay 622 attracts its armatures and closes a circuit from ground through its left front contact, winding of relay 620 to battery. bRelay 620 operates and a circuit is established from battery through the winding of relay 621, left contact of relay 620, right contact of relay 622 to ground. Relay 620 also causes, as previously explained, the operation of relay 711. llith relays 621 and 711 operated the start circuit is now extended from ground through the outermost right contact of relay 618, right armature and back contact of relay 619, inner' right front contact of relay 621, conductor 647, Contact' 713 of relay 711, and thence to the allotting relay of the first idle register sender in the second group, as previously traced. Assuming the 'first sender to be idle, the allotting relay 709 is operated and completes a circuit Afrom batterythrough its winding and right Contact, conductor 717, contact 720 of relay 711, conductor 650, outer right front contact of relay 621, winding of relay 619, to ground at the outermost right contact of tra' 

